The importance of preventing mental health disorders in workers has been increasing in Japan (Ministry of Health, Labour and Welfare, 2016). The Japanese government passed legislation that revised the Industrial Safety and Health Act such that, beginning in December 2015, business establishments with more than 50 employees are now required to conduct medical examinations (stress checks) of all employees (Ministry of Health, Labour and Welfare, 2014). This stress check system is aimed at preventing mental health issues in the workforce, promoting awareness of stress in the workers themselves, and amelioration of stress in the work environment (Ministry of Health, Labour and Welfare, 2016). The results of a field survey of industrial safety and health by the Ministry of Health, Labour and Welfare in 2016 revealed that 59.5% of employees had work-related issues that might cause high levels of stress, distress, and anxiety (Ministry of Health, Labour and Welfare, 2017a). The fact sheet on workers’ compensation for overwork-death and stress-death announced by the Ministry of Health, Labour and Welfare in 2017 reported that the number of workers’ compensation claims for mental disorders caused by work-related psychological strain was on the increase (Ministry of Health, Labour and Welfare, 2017b). The adoption of greenery into the office environment is becoming widespread as the need for improving mental health becomes greater. Many studies have been done on the psychological and physiological effects on workers of having indoor plants in the work environment. The outcomes addressed in these studies have been wide-ranging. Dravigne et al. (2008) reported positive effects from the presence of office plants, window views of green spaces, or both on job satisfaction and also on the overall quality of life of office workers. Other studies have focused on more specific aspects of human health: mood (Larsen et al., 1998; Shibata and Suzuki, 2001, 2002, 2004), perceived stress (Bringslimark et al., 2007; Dijkstra et al., 2008; Genjo and Matsumoto, 2016; Lohr et al., 1996), health and discomfort symptoms including fatigue (Fjeld, 2000; Shibata and Suzuki, 2001), productivity (Bringslimark et al., 2007; Larsen et al., 1998; Lohr et al., 1996; Matsumoto and Genjo, 2012), task performance (Shibata and Suzuki, 2001, 2002, 2004), attention capacity (Raanaas et al., 2011), and workplace satisfaction (Nieuwenhuis et al., 2014).
In addition to looking at different human impact outcomes, studies have been conducted that focused on specific independent variables. Researchers examined the size and volume of greenery (Nishina, 2008); the number of plants installed (Imanishi et al., 2002; Larsen et al., 1998); the kinds of plants (Genjo and Matsumoto, 2016; Imanishi et al., 2002); the shape, size, and distance of the plants from the participant (Hasegawa and Shimomura, 2011); and the index of greenness of an interior space (Choi et al., 2016). Most of these studies were conducted in laboratory or quasi-office settings.
A more limited number of studies targeting office workers in real office settings have also been conducted (Bringslimark et al., 2007; Fjeld, 2000; Genjo and Matsumoto, 2016; Imanishi et al., 2002; Matsumoto and Genjo, 2012; Nieuwenhuis et al., 2014; Nishina, 2008; Yadomaru et al., 2016). In these studies, indoor plants were placed on the floor, windowsills, shelves, desks, or all of these options in the office to provide visual access to the plants.
Some earlier studies reported that the presence of indoor plants in the workplace was conducive to positive psychological (Fjeld, 2000) and physiological effects (Lohr et al., 1996; Matsumoto and Genjo, 2012). On the other hand, Bringslimark et al. (2007) reported that the greater the number of plants placed within 1 m of a participant's desk, the greater the level of perceived stress. Larsen et al. (1998) also reported that with an increase in the number of plants in the office there was a corresponding decrease in performance on a letter identification productivity task. They compared three plant conditions: without plants, with a moderate number of plants (occupying 7.16% of the total cubic office space), and with a high number of plants (occupying 17.88% of the total cubic office space).
Most of the previously mentioned studies focused on the psychological and physiological effects of passive interaction with the plants. Nishina (2008) studied the effects of active involvement with plants. He reported that allowing the participants to choose and care for the plants in the study enhanced their satisfaction and contributed to the mitigation of stress in the workplace.
The objective of this study was to verify the stress-reducing effect of gazing intentionally at a plant in a real office setting when a worker felt fatigue during office hours. Each plant used in the study was chosen and cared for by the worker. As many previous studies have substantiated, both passive and active involvement with plants in the workplace contributes to mitigation of office worker stress and fatigue. In our study, the participants were provided daily visual access to plants by having plants on their desks (a passive involvement with plants). They also had the opportunity to choose and to care for those plants (an active involvement with plants). Furthermore, we considered that intentionally gazing at the plants was an active, but not physical, involvement with plants that office workers could do quickly and easily at their desks.
Our hypothesis was that a small plant on a desk had the potential to reduce stress 1) by allowing participants to transfer their gaze intentionally to the plant and to have a rest without cognitive engagement, and 2) by providing participants the opportunity to take care of a plant that they themselves chose. We chose to use small plants that did not take up very much workspace. Our study sought to explore the practical use of indoor plants to benefit the mental health of office workers.
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